Eye contact is a key part of human interaction. People look in each other's eyes to determine interest and distraction. A human interaction with a machine can feel more natural or more human, when the machine is able to determine what the human is looking at. This may be used primarily to determine where the human's attention is directed. If a person is looking at a machine interface, then the machine can use this information to provide an appropriate response. When the person is looking away, then the machine can wait for the person's attention to return or can call to the person to return. If the person is looking at a particular object, then the machine can present some interaction with that object.
In several systems, a person's direction of attention is determined by observing the person's eyes through a camera and then analyzing images of the eyes to determine a direction for the person's pupils. Since eyes generally have a white background with a dark iris and even darker pupil, the position of the pupil can be determined with relative ease. The eye direction or gaze direction may then be used as in input into a user interface or used as a user interaction.